A lot do come out and are correct, but a lot if the time people see things that aren't really there and will stage entire theories around a single insignificant detail.
Um, I remember the prediction from 2 manga chapters back came true. Someone posted it was time the SO6P was revealed into the series and the prediction was right. So yea they do but not a lot, often you will see parts of theorys resemble whats acutally going on in the manga chapter.
theories in NB could potentially encompass every sensible possibilities the chapters can go when we view them as a whole. some of them has the correct prediction and some don't
a few narutobase theories do turn out to come true..
chatte a year or so ago predicted sakura would get the yin seal on her forehead as her forehead was also pointed out and that it was a foreshadowing by kishi.. a lot of people disagreed and what do you know a year or so later sakura gets the yin seal :|
this is just one of a few theories..
honestly though.. some of the theories on here are better and make more sense then what kishi does